The embodiments described herein relate to medicament delivery devices. More particularly, the embodiments described herein relate to medicament delivery devices for delivery of medicaments contained within a prefilled syringe.
Known prefilled syringes are commonly used to contain and inject medicaments. Known prefilled syringes include a syringe body, often constructed from glass, within which a medicament is contained. The distal end portion of some known prefilled syringes includes a staked needle (i.e., a needle that is permanently coupled to the syringe body during manufacture), the end of which is disposed within a needle cover to maintain the sterility of the needle prior to use. Other known prefilled syringes include a Luer fitting or adapted such that the distal end portion of the syringe body can be coupled to a needle. The proximal end portion of the syringe body of known prefilled syringes includes a plunger (usually constructed from an elastomer) that defines a portion of the container closure, and that can be moved within the syringe body to inject the medicament. The proximal end portion also includes a flange to allow the user to grasp the syringe body and manually apply a force to a piston to move the plunger, thereby causing injection of the medicament.
Although prefilled syringes can be cost effective devices for storing and delivering medicaments, known methods for using prefilled syringes include manually inserting the needle into the body followed by manually applying the injection force. Moreover, upon completion of the injection, known methods include covering the needle to avoid needle sticks. Thus, known prefilled syringes are often used by healthcare professionals that are trained in such procedures. To facilitate the self-administration of medicaments contained in prefilled syringes, some known autoinjectors have been adapted to contain prefilled syringes. In this manner, the autoinjector provides a source of stored energy for inserting the needle and/or injecting the medicament.
Known autoinjectors, however, are often designed for a medicament container having a specific size and/or shape, and are therefore often not configured to receive known prefilled syringes. For example, using a prefilled syringe within a known autoinjector can often result in high forces being applied to the flange of the syringe body during the insertion operation, which can lead to breakage of the syringe flange or body. Moreover, because many known prefilled syringes include a staked needle that is in fluid communication with the medicament, applying a force to the plunger during storage and/or during an insertion operation is undesirable. For example, the application of a force against the plunger during storage, which can result, for example, when a spring-loaded member is placed in contact with the plunger, can cause in leakage of the medicament. As another example, the application of a force against the plunger during a needle insertion event can result in the injection of the medicament before the needle is inserted to the desired location. Similarly stated, some known auto-injectors are not configured to control the force applied to the plunger within the syringe body during storage and/or needle insertion.
Known autoinjectors configured to incorporate a prefilled syringe often include a spring-based actuation system that moves a piston rod to insert the needle and inject the medicament. The size (e.g., length) of such known systems, however, can be larger than desired because of the need to incorporate the piston rod.
Moreover, known medicaments or therapeutic substances are formulated to include high molecular weight compounds, compounds with complex molecular structures, living cells, and/or biologics. Such medicaments often have a very high viscosity (e.g., greater than about 100 centipoise at room temperature), which must be accommodated by the delivery system. Accordingly, many know auto-injectors that accommodate a prefilled syringe may not be able to provide sufficient force and/or develop the desired flow rate for effective delivery.
Thus, a need exists for improved methods and devices for delivering medicaments contained within a prefilled syringe.